One important element in modern petroleum, natural gas and geothermal drilling is data acquisition during the drilling process; however, the same also applies to the construction of the drill hole and the subsequent petroleum, natural gas and hot water production. Only by acquiring the respective relevant measurement quantities can drilling be pursued safely, efficiently and economically. One problem arises in real time data transmission of measurement data to the surface of the drilling rig. Data are to be transmitted at a high data rate (for example, 200 kBaud) from several kilometers deep.
Currently, simple steel pipes without cabling are used to some extent on drilling rigs. The pipes are coupled at regular intervals (for example, 9 meters). In this way, a drilling column that is several kilometers long is formed on whose end the drilling bit is located. Within the pipes is the flush fluid (rinsing fluid) that performs many kinds of functions during the drilling process. One of these functions in the prior art is the transmission of data by means of pressure pulses. Since this communication is very slow (for example, 10 baud), methods have been increasingly sought that use other transmission mechanisms (sonar, currents via the ground, etc.). Approaches that are associated with cabling of the drilling column have proven most efficient (current, light, etc.). As soon as the drilling column is connected by means of electrical cables or conductive layers, high-speed data transmission is possible.
Here, fundamentally two methods are possible. Some prototypes work with galvanic connections between the individual pipes of the column. Systems that are to some extent commercially available use a magnetic coupling between the pipes. The magnetic coupling that is currently in use allows only data transmission.
The intention to cable a drill string encounters several problems at the same time.
Steel pipes must be produced or retrofitted with pressure-proof, mud-resistant and heat-resistant cables without the bearing strength of the drill string being influenced and without personnel being hindered in screwing the pipes together.
In order to enable data transmission in the drill string, the problem of the electrical connection between the pipes must be solved. The electrical connection must be produced reliably, easily and durably in the mechanical connection of the pipes (rotary motion). The greatest challenge in making an electrical connection that can transmit current and/or data is the screwing motion during the screw connection process of the individual drilling column (pipes). Moreover, the drilling process constitutes a harsh environment, due to extensive fouling and liquids of all type. This challenge is to be overcome in order to develop a successful system that is ready for use.